Method for manufacturing a droplet discharge head

ABSTRACT

In the method for manufacturing a droplet discharge head, a mold  100 , including a convexity portion having convexities which have the substantially same shape as a liquid chamber including pressure chambers  21  and nozzle sections  21   b , is prepared. A slurry SL is filled into the mold  100 , and the mold  100  is placed on a porous plate  120 . A solvent included in the slurry permeates into fine pores of the porous plate. Accordingly, the slurry is dried, so that a compact-after-dried  110  is formed. Thereafter, a vibration plate, and the like are joined to the compact, and the compact is fired. Further, piezoelectric elements, and the like are formed on the pressure chambers.

FIELD OF THE INVENTION

The present invention relates to a method for manufacturing a droplet discharge head, which discharges a droplet of, for example, a liquid containing DNA, a liquid material, a liquid fuel, and the like.

BACK GROUND OF THE INVENTION

Conventionally, a ceramic layered body having in its inside a hollow cavity, which is, for example, a pressure chamber for pressurizing a liquid, has been known. Such a ceramic layered body is used in a wide variety of fields including, for example, an apparatus for producing a DNA chip, an “actuator for injecting a fluid” such as a fuel injection device, an actuator for an ink jet printer, a solid-oxide fuel cell (SOFC), a switching device, a sensor, and so on (refer to Patent document 1).

Generally, such a ceramic layered body is manufactured according to procedures described below.

(1) Ceramic green sheets are prepared.

(2) A through hole having a predetermined shape is formed in the ceramic green sheet by punching using “a mold and a die”.

(3) The ceramic green sheets each having the formed through hole and the ceramic green sheets each having no through hole are stacked (layered).

(4) A plurality of the layered green sheets are fired to be united (integrated).

RELATED ART Patent Document

-   [Patent Document 1] Japanese Patent No. 3600198

SUMMARY OF THE INVENTION

However, punching using a mold and a die forms the through hole by sheering. Accordingly, when the ceramic green sheet is punched through, a large force is applied to the ceramic green sheet. As a result, a fracture surface becomes rough, or a burr and a crack may be generated. Especially, when the pressure chamber (cavity) is miniaturized, the deformation, the burr, the crack, and the like may cause great adverse effects on a shape accuracy of the pressure chamber (cavity). Further, “the mold and the die” need to have hardness to endure the punching, and therefore, they are formed of a material having high hardness. Since it is difficult to produce a miniaturized mold and a miniaturized die using the material having high hardness, there is a limit on miniaturizing the pressure chamber (cavity).

The present invention is made to cope with the problems described above. That is, one of the objects of the present invention is to provide a “method for manufacturing a droplet discharge head”, which allows to manufacture a droplet discharge head having an excellent shape accuracy, even if the pressure chamber is miniaturized, a distance between the pressure chambers adjacent to each other is short, and so on.

One of the methods for manufacturing a droplet discharge head (hereinafter, referred to as a “present manufacturing method”) according to the present invention in order to achieve the object described above is a manufacturing method for manufacturing a droplet discharge head including a “droplet discharge head body comprising a pressure chamber for retaining/storing liquid and a nozzle section communicating with the pressure chamber”.

The present manufacturing method includes (1) slurry preparing step, (2) mold preparing step, (3) porous plate preparing step, (4) head-body-before-fired forming step, and (5) firing step.

(1) Slurry Preparing Step:

The slurry preparing step is a step for preparing a slurry including ceramic powders, a solvent (resolvent) for the ceramic powders, and an organic material.

(2) Mold Preparing Step:

The mold preparing step is a step for preparing a mold including a base portion having at least one flat (plain) surface, and a convexity portion having a convexity which stands (is held upright, or erects) from the flat surface of the base portion and has the substantially same shape as a “liquid chamber including the pressure chamber and the nozzle section”. A molding surface of the mold is composed of a portion of the flat surface of the base portion at which the convexity portion does not exist, and a surface of the convexity portion.

(3) Porous Plate Preparing Step:

The porous plate preparing step is a step for preparing a porous plate, having at least one flat (plain) surface, through which gases can pass.

(4) Head-Body-Before-Fired Forming Step:

The head-body-before-fired forming step is a step for forming a droplet discharge head body-before-fired (droplet discharge head body which has not been fired) by placing the porous plate and the mold in such a manner that the porous plate and the mold are opposed to each other while the slurry is maintained (or kept, held) between the flat surface of the porous plate and the molding surface of the mold, and drying the slurry through having the solvent included in the slurry permeate into fine pores of the porous plate.

(5) Firing Step:

The firing step is a step for forming a droplet discharge head body-after-fired (droplet discharge head body which has been fired) by firing the droplet discharge head body-before-fired.

As long as the slurry preparing step, the mold preparing step, and the porous plate preparing step are performed before the head-body-before-fired forming step, these steps can be performed in any order.

According to the present manufacturing method, the pressure chamber is formed by forming the slurry in the mold. Therefore, the droplet discharge head having an excellent shape accuracy can be manufactured, even when the pressure chamber is miniaturized, the distance between the pressure chambers adjacent to each other is short, and so on.

Further, according to the present manufacturing method, the nozzle section is also formed by forming the slurry in the mold. Therefore, the surface of the nozzle section is smooth and has no burrs or the like, as compared with the case in which the nozzle section is formed by punching using a mold and a die. As a result, the droplet discharge head capable of stably discharging droplets can be provided.

According to the present manufacturing method, the droplet discharge head body is formed (made, produced) using a single mold. It is therefore unnecessary to join two compacts to form the droplet discharge head body, and further unnecessary to join a metal plate, or the like, which has a through hole, to the nozzle section of the droplet discharge head body, for example. Thus, the steps can be simplified. Further, it is unnecessary to pressure bond or join two compacts while aligning those two compacts in order to form the droplet discharge head body. Therefore, the droplet discharge head having a desired shape can easily be manufactured.

Further, it is preferable that the head-body-before-fired forming step include:

polishing-before-demolding step for polishing, in a state in which (while) a compact-after-dried formed of the slurry which was dried in the mold is maintained (kept, held) in the mold, an exposed surface of the compact-after-dried (i.e., surface of the compact which contacted with the flat surface of the porous plate), to thereby remove (eliminate) a remnant membrane (remained residual film) of the compact-after-dried to complete (form) a portion corresponding to the nozzle section; and

demolding step for releasing (separating, removing) the mold from the compact-after-dried from which the remnant membrane was removed.

According to the method described above, polishing the compact-after-dried is preformed in a state in which a “hollow cavity portions of the compact-after-dried” which will become the pressure chamber and the nozzle section are buried in (or filled with) the (portion of the) mold, grinding sludge and/or abrasive grains do not enter into the hollow cavity portions. It is therefore unnecessary to include such a step for removing (eliminating) the grinding sludge and/or abrasive grains. Consequently, the manufacturing method as a whole can be simplified. Furthermore, the “compact-after-dried” to be polished is the compact which has not been fired yet, and thus, it has lower hardness than a compact which has been fired (fired body). Accordingly, a polishing rate can be increased, and therefore, the polishing can be completed within short time.

In addition, the polishing-before-demolding step may be a step for polishing the exposed surface of the compact-after-dried by holding (retaining) the mold, maintaining (keeping, holding) the compact-after-dried, at an side opposite to the molding surface by a polishing retainer (holding tool for polishing), and pressing the exposed surface of the compact-after-dried against a polishing plate while the polishing retainer is reciprocated in a direction parallel to the flat surface of the base portion.

According to the method described above, since the polishing is performed with using the portion of the mold opposite to the molding surface (the surface opposite to the molding surface, back surface of the mold) as a reference, a flatness of the exposed surface of the compact-after-dried (surface to be polished) can be easily ensured.

Meanwhile, the present manufacturing method may further include:

special blast processing using elastic body step, performed after the firing step, for projecting (injecting) polishing agents, each including a plurality of abrasive grains being smaller than and fixed to an elastic base material, to the droplet discharge head body-after-fired to thereby remove (eliminate) the remnant membrane (remained residual film) of the droplet discharge head body-after-fired to complete/finish a portion corresponding to the nozzle section.

According to the blast processing described above, even when the droplet discharge head body-after-fired has small undulation/warpage caused by being fired, the droplet discharge head body-after-fired can be polished by a constant amount according to the undulation/warpage. Therefore, a diameter of a tip portion of the nozzle section (i.e., opening for droplet discharge, which is formed on the surface of the head body-after-fired by the nozzle section) can be controlled within a desired range. In addition, a surface roughness in the vicinity of the opening(s) for droplet discharge can be uniform, and therefore, a hydrophilicity of the lower surface of the droplet discharge head body in the vicinity of the opening(s) for droplet discharge to a liquid can be uniform. Accordingly, the droplet discharge head capable of discharging the droplets stably can be manufactured.

The above and other objects, features and associated advantages of the present invention will be easily understood better from the following description of each of embodiments according to the present invention with reference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 includes (A) being a plan view of a droplet discharge head body manufactured using a method for manufacturing a droplet discharge head of an embodiment according to the present invention, and (B) being a cross-sectional view of the droplet discharge head manufactured using the manufacturing method;

FIG. 2 includes (A) being a vertical cross-sectional view of a mold used in one aspect of the manufacturing methods, along a longitudinal direction (direction along a longer side) of the mold, (B) being a vertical cross-sectional view of the mold in a direction along a shorter side of the mold, and (C) being a partial perspective view of the mold;

FIG. 3 is a view for describing “a porous plate preparing step and a compact forming step” of the aspect of the manufacturing method;

FIG. 4 is another view for describing the compact forming step of the aspect of the manufacturing method;

FIG. 5 is another view for describing the compact forming step of the aspect of the manufacturing method;

FIG. 6 is a cross-sectional view of the compact which is formed through the compact forming step of the aspect of the manufacturing method;

FIG. 7 is a cross-sectional view of the droplet discharge head manufactured according to the aspect of the manufacturing method;

FIG. 8 is a partially magnified photograph of the droplet discharge head body manufactured according to the aspect of the manufacturing method;

FIG. 9 is a view for describing a way to remove a remnant membrane in a modified example of the manufacturing method;

FIG. 10 is a cross-sectional view of a head body-before fired formed according to the modified example shown in FIG. 9;

FIG. 11 is a view for describing another way to remove a remnant membrane in another modified example of the manufacturing method;

DESCRIPTION OF THE EMBODIMENTS CARRYING OUT THE INVENTION

Next will be described a method for manufacturing a droplet discharge head according to embodiment of the present invention with reference to the drawings. It should be noted that performing order of the steps described below can be changed as long as there is no inconsistency.

<Structure>

First, a schematic structure will be described of a droplet discharge head 10 manufactured by a “method for manufacturing a droplet discharge head” according to an embodiment of the present invention.

As shown in (A) and (B) of FIG. 1, the droplet discharge head 10 comprises a droplet discharge head body (head body) 20, a vibration plate 30, a liquid storage chamber cover member 40, and a plurality (in the example shown in FIG. 1, nine) of piezoelectric elements 50. It should be noted that (A) of FIG. 1 is a plan view of the droplet discharge head 10 (that is, the head body 20) which is in a state in which the vibration plate 30, the liquid storage chamber cover member 40, and a plurality of the piezoelectric elements 50 are removed. (B) of FIG. 1 is a cross-sectional view of the droplet discharge head 10 cut by a plane along 1-1 line shown in the (A) of FIG. 1.

The head body 20 is formed of ceramic. The head body 20 has a rectangular parallelepiped shape having sides, each being parallel to one of X, Y and Z axes orthogonal to each other. That is, as shown (A) of FIG. 1, a shape of a planar view of the head body 20 (shape obtained when the head body 20 is viewed from a positive Z axis side along the Z axis) is rectangular. Long sides and short sides of the rectangle are parallel to the X axis and the Y axis, respectively. A direction of a thickness (height) of the head body 20 is parallel to the Z axis. It should be noted that, for convenience of description, a positive direction of the Z axis is defined as an upper direction, and a negative direction of the Z axis is defined as a lower direction, hereinafter.

A plurality (in the example shown in FIG. 1, nine) of groove sections (channels) 21 a are provided (formed) which constitute a plurality of the pressure chambers 21, at an upper portion of the head body 20. A plurality of the groove sections 21 have the same shape as each other. Each of the groove sections 21 has a substantially rectangular parallelepiped shape.

More specifically, the groove section 21 a has “long sides, each extending along the X-axis, and short sides, each extending along the Y-axis”, in a plan view. One of ends of the long side extending along the X-axis, of the groove section 21 a is positioned at a position close to an X-axis negative direction end of the head body 20. The other one of the ends of the long side, extending along the X-axis, of the groove section 21 a is positioned at a substantially center portion of the head body 20 in an X-axis direction. A bottom surface of the groove section 21 a is a flat (plain) surface located at a substantially center portion of the head body 20 in a thickness direction of the head body 20. That is, a depth (height) of the groove section 21 a is about a half of the thickness (height) of the head body 20.

In the head body 20, nozzle sections 21 b are formed. Each of the nozzle sections 21 b are provided at a position close to an X-axis negative direction end of the bottom surface of the groove section 21 a. Each of the nozzle sections 21 b has an inverted circular truncated cone shape (or a cylindrical shape). Each of the nozzle sections 21 b provides a communication passage between the respective bottom surface of each of the groove sections 21 a and the lower surface 20 a of the head body 20. Thus, each of the nozzle sections 21 b forms (provides) a droplet discharge hole.

A concave section 22 a is formed for constituting (forming) a liquid storage chamber (ink tank chamber) 22 at the upper portion of the head body 20. The concave section 22 a has a substantially rectangular parallelepiped shape.

More specifically, the concave section 22 a has “long sides, each extending along the X-axis, and short sides, each extending along the Y-axis”, in a plan view. One of ends of the long side, extending along the X-axis, of the concave section 22 a is positioned at a position close to an X-axis positive direction end of the head body 20. The other one of the ends of the long side, extending along the X-axis, of the concave section 22 a is positioned at the substantially center portion of the head body 20 in the X-axis direction, and is apart from the other one of the ends of the long side, extending along the X-axis, of the groove section 21 a at a predetermined distance. One of the ends of the short side, extending along the Y-axis, of the concave section 22 a is positioned at a portion in the side of a Y-axis positive direction as compared to a Y-axis positive direction end of the short side of the groove section 21 a which is positioned at the Y-axis positive direction end of the plurality of the groove sections 21 a. The other one of the ends of the short side, extending along the Y-axis, of the concave section 22 a is positioned at a portion in the side of Y-axis negative direction as compared to a Y-axis negative direction end of the short side of the groove section 21 a which is positioned at the Y-axis negative direction end of the plurality of the groove sections 21 a. A bottom surface of the concave section 22 a is a flat (plain) surface located at the substantially center portion of the head body 20 in the thickness direction of the head body 20. That is, a depth (height) of the concave section 22 a is the same as the depth (height) of the groove section 21 a.

A plurality (in the example shown in FIG. 1, nine) of groove sections (channels) 23 a are provided (formed) which constitute a plurality of liquid flow holes 23 at the upper portion of the head body 20. Each one of the groove sections 23 a is provided so as to correspond to each one of the groove sections 21 a. A plurality of the groove sections 23 a have the same shape as each other. Each of the groove sections 23 a has a substantially rectangular parallelepiped shape.

More specifically, each of the groove sections 23 a has “long sides, each extending along the X-axis, and short sides, each extending along the Y-axis”, in a plan view. One of ends of the long side extending along the X-axis, of each of the groove sections 23 a is extended to the “short side extending along the Y-axis” of one of the groove sections 21 a, located at the X-axis positive direction end of the one of the groove sections 21 a. The other one of the ends of the long side, extending along the X-axis, of each of the groove sections 23 a is extended to the “short side extending along the Y-axis” of the concave section 22 a, located at the X-axis negative direction end of the concave section 22 a. A length of the short side extending along the Y-axis of each of the groove section 23 a is smaller than a length of the short side extending along the Y-axis of each of the groove sections 21 a. Each one of the groove sections 23 a provides a communication passage between each one of the groove sections 21 a and the concave section 22 a. A bottom surface of each of the groove sections 23 a is a flat (plain) surface located at the substantially center portion of the head body 20 in the thickness direction of the head body 20. That is, a depth (height) of the groove section 23 a is the same as the depth (height) of the groove section 21 a.

The vibration plate 30 is a thin plate formed of a ceramic, having a small thickness (height) along the Z-axis direction. The vibration plate 30 is easily deformable. A shape of the vibration plate 30 in a plan view is a rectangle. A position of an X-axis positive direction end of the vibration plate 30 substantially coincides with the position of the X-axis positive direction ends of the groove sections 21 a. A position of an X-axis negative direction end of the vibration plate 30 substantially coincides with the position of the X-axis negative direction end of the head body 20. “A Y-axis positive direction end and a Y-axis negative direction end” of the vibration plate 30 substantially coincide with “the Y-axis positive direction end and the Y-axis negative direction end” of the head body 20, respectively. The vibration plate 30 is disposed so as to contact with an upper surface of the head body 20. Accordingly, the vibration plate 30 covers upper portions of all of the groove sections 21 a. Consequently, each of the pressure chambers 21 is formed (defined) by the bottom surface and side surfaces of each of the groove sections 21 a together with a lower surface of the vibration plate 30.

The liquid storage chamber cover member 40 is a plate formed of a ceramic, having a thickness (height) along the Z-axis direction. A shape of the liquid storage chamber cover member 40 in a plan view is a rectangle. A position of an X-axis positive direction end of the liquid storage chamber cover member 40 substantially coincides with the position of the X-axis positive direction ends of the head body 20. A position of an X-axis negative direction end of the liquid storage chamber cover member 40 coincides with the position of the X-axis positive direction end of the vibration plate 30. That is, the X-axis negative direction end of the liquid storage chamber cover member 40 contacts with the X-axis positive direction end of the vibration plate 30. “A Y-axis positive direction end and a Y-axis negative direction end” of the liquid storage chamber cover member 40 substantially coincide with “the Y-axis positive direction end and the Y-axis negative direction end” of the head body 20, respectively. The liquid storage chamber cover member 40 is disposed so as to contact with the upper surface of the head body 20. Accordingly, the liquid storage chamber cover member 40 covers an upper portion of the concave section 22 a. Consequently, the liquid storage chamber 22 is formed (defined) by the bottom surface and side surfaces of the concave section 22 a together with a lower surface of the liquid storage chamber cover member 40.

Further, the liquid storage chamber cover member 40 covers upper portions of all of the groove sections 23 a. Consequently, each of the liquid flow holes 23 is formed (defined) by the bottom surface and side surfaces of each of the groove sections 23 a together with the lower surface of the liquid storage chamber cover member 40. Each one of the liquid flow holes 23 provides a liquid passage which allows a liquid to flow (pass) between each one of the pressure chambers 21 and the liquid storage chamber 22.

A liquid supply through hole 40 a is formed in the liquid storage chamber cover member 40. The liquid supply through hole 40 a is provided at a substantially central portion of the liquid storage chamber cover member 40 in a plan view. The liquid supply through hole 40 a provides a liquid passage which allows a liquid to flow (pass) between an exterior of the droplet discharge head body 20 and the liquid storage chamber 22.

It should be noted that, in place of the liquid storage chamber cover member 40, the vibration plate 30 may cover not only the upper portions of all of the concave portions 21 a but also the upper portions of concave portion 22 a and all of the groove sections 23 a.

Each of a plurality of the piezoelectric elements 50 has “long sides, each extending along the X-axis, and short sides, each extending along the Y-axis”, in a plan view. A shape of each of the piezoelectric elements 50 substantially coincides with the shape of each of the pressure chambers 21 (and thus, coincides with each of the groove sections 21 a), in a plan view. Each of a plurality of the piezoelectric elements 50 is formed so as to oppose to each of a plurality of the pressure chambers 21 to sandwich the vibration plate 30 therebetween.

In the thus configured droplet discharge head 10, a liquid (e.g., ink) is supplied from the exterior of the droplet discharge head 10 to the liquid storage chamber 22 through the liquid supply through hole 40 a. The liquid in the liquid storage chamber 22 is supplied to each of the pressure chambers 21 through each of the liquid flow holes 23. When the piezoelectric element 50 is deformed by means of an electric power supplied from an unillustrated power/drive source, the vibration plate 30 deforms. Consequently, the liquid in the pressure chamber 21 is pressurized (compressed) to thereby be discharged as a droplet from the lower surface 20 a of the droplet discharge head 10 through the “nozzle section 21 b providing a communication passage between the pressure chamber 21 to the exterior”. That is, the liquid is discharged from the opening for discharging a liquid, the opening being a lower end of the nozzle section 21 b formed on the lower surface 20 a.

<Manufacturing Method>

The manufacturing method will next be described for each of steps.

(Slurry Preparing Step)

Firstly, a slurry SL is prepared. The slurry SL consists of ceramic powders serving as particles of a main raw material, a solvent for the ceramic powders, an organic material, and a plasticizing agent. A ratio by weight of those is, for instance, the ceramic powder:the solvent:the organic material:the plasticizing agent=100:50-100:5-10:2-5. In the present example, the ceramic powders are made of alumina, zirconia, and so on. The solvent is made of toluene, isopropyl alcohol, and so on. The organic material is made of polyvinyl butyral, and so on. The plasticizing agent is made of phthalate series butyl, and so on. Each of the materials and the weight ratio are not limited thereto. It should be noted that it is preferable that a viscosity of the slurry be, for example, 0.1-100 Pa·sec.

(Mold Preparing Step)

A mold (a pressing mold, a stamper) 100 shown in (A) to (C) of FIG. 2 is prepared. The (A) of FIG. 2 is a cross-sectional view of the mold 100 cut by a plane (X-Z plane) along a longitudinal direction (the X-axis direction) of the mold 100. The (B) of FIG. 2 is a cross-sectional view of the mold 100 cut by a plane (Y-Z plane) along a shorter side (Y-axis direction) of the mold 100 at a “predetermined position in the side of the X-axis negative direction with respect to a central portion in the X-axis direction of the mold 100”. The (C) of FIG. 2 is a partial perspective view of the mold 100. The mold 100 comprises a base portion 101, convexity portions for forming pressure chambers 102, convexity portions for forming nozzle sections 103, and a frame portion 104.

The base portion 101 is a substantially flat plate. Therefore, the base portion 101 comprises at least one flat (plain) surface 101 u.

The convexity portions for forming pressure chambers 102 stand (are held upright, or erect) from the flat surface 101 u. The convexity portions for forming pressure chambers 102 have the substantially same shape as a shape defined by “a plurality of the groove sections 21 a, the concave section 22 a, and a plurality of the groove sections 23 a” described above. That is, the convexity portions for forming pressure chambers 102 have the substantially same shape as a shape defined by “a plurality of the pressure chambers 21, the liquid storage chamber 22, and a plurality of the liquid flow holes 23”. Thus, the convexity portions for forming pressure chambers 102 are a convexity portion including convexities, each having the substantially same shape as the shape of each of the pressure chambers 21 that are arranged parallel to each other.

Each of the convexity portions for forming nozzle sections 103 stands (is held upright, or erects) from a top surface 102 a of each of the convexity portions for forming pressure chambers 102. Each of the convexity portions for forming nozzle sections 103 has the substantially same shape as the shape of each of the nozzle sections 21 b shown in FIG. 1. That is, each of the convexity portions for forming nozzle sections 103 has a circular truncated cone shape. Accordingly, the mold 100 can be said that it has a convexity portion including convexities having the substantially same shape as a shape of a “liquid chamber including a plurality of the pressure chambers 21, and a plurality of the nozzle sections 21 b (plus, the liquid storage chamber 22, and a plurality of the liquid flow holes 23)”.

The frame portion 104 stands (is held upright, or erects) from the flat surface 101 u at an entire outer circumference of the base portion 101. A shape defined by inner side surfaces of the frame portion 104 is the substantially same as the shape defined by the outer circumference of the head body 20 shown in FIG. 1. A top surface 104 a of the frame portion 104 and each of top surfaces 103 a of each of the convexity portions for forming nozzle sections 103 exist on a single plane PL parallel to the flat surface 101 u.

A molding surface of the mold 100 is composed of a portion (surface) of the flat surface 101 u of the base portion 101 where “the convexity portions for forming pressure chambers 102 and the frame portion 104” do not exist, a portion (surfaces) of the surfaces of the convexity portions for forming pressure chambers 102 where the convexity portions for forming nozzle sections 103 do not exist, surfaces of the convexity portions for forming nozzle sections 103, and the inner side surfaces of the frame portion 104.

It is preferable that the molding surface of the mold 100 be coated with a mold release agent. In this case, in order to improve adherence force between the mold 100 and the mold release agent, it is preferable that the mold 100 (molding surface of the mold 100, that is, mold release surface) be cleaned before the mold release agent is applied to the mold 100. The cleaning can be performed by an ultrasonic cleaning, an acid cleaning, an UV ozone cleaning, and so on. Preferably, the molding surface to be coated with the mold release agent (i.e. a cleaned surface) is cleaned at the atomic level. One of examples of the mold release agent is a fluorine series mold release agent such as “OPTOOL DSX” available from DAIKIN INDUSTRIES, Ltd. The mold release agent may be a silicon series mold release agent or a wax release agent. The mold release agent is applied by dipping, spraying, brushing and so on, and thereafter, is formed in the form of a film on the surface (molding surface) of the mold 100 through a drying step and a washing step. The surface of the mold 100 may be coated by an inorganic film treatment with a DLC (Diamond Like Carbon) coating. Further, the surface of the mold 100 may be coated by a combination of the inorganic film treatment and the mold release agent treatment.

(Porous Plate Preparing Step)

A porous plate 120 through which gases can pass is prepared (refer to FIG. 3). At least one surface 120 u of surfaces of the porous plate 120 (in actuality, both surfaces) is flat (plain). One of typical examples of the porous plate 120 is a porous film formed of resin. A diameter of the fine pore (an averaged diameter of the fine pores, fineness) of the porous plate 120 is smaller than a particle diameter (an averaged particle diameter) of the ceramic powder, but is larger than a diameter of a molecule of the solvent. More specifically, the porous plate 120 is a porous film formed of, for example, “polypropylene, polyolefin, and the like” whose diameter of the fine pore is equal to or smaller than 1 μm (more preferably, 0.5 μm). It should be noted that the porous plate 120 may be a porous ceramic substrate, a porous metal (e.g., sintered metal) substrate, and so on.

(Compact Forming Step)

As shown in FIG. 3, the slurry SL is filled into an inside of the frame portion 104 of the mold 100. The slurry SL is filled by applying. This step is also referred to as a “slurry filling (or applying) step”. The slurry SL may be filled by any of appropriate methods other than applying (e.g., dipping, squeegeeing, brushing, and filling with a dispenser, etc.). Further, in order to improve a filling rate of the slurry, ultrasonic vibration may be applied to the mold 100, or air bubbles remaining in the mold 100 may be removed by a vacuum deaeration, when filling the slurry SL into the inside of the frame portion 104. Further, the slurry SL may be filled into the mold 100 by “impressing (pressing, pushing) the mold 100 onto (against) a plate which is separately prepared” while holding (maintaining) the slurry SL between the mold 100 and the plate. The plate may be a PET film or the like to which a mold release treatment has been applied in order to avoid a transfer of the slurry SL to the plate (that is, in such a manner that the “slurry SL filled in the mold 100” does not remain on the plate when the mold 100 is released/separated from the plate).

In this slurry filling step, the slurry SL is filled into the mold 100 in an amount more than necessary (i.e., an excessive amount of slurry SL is filled). This is because, a pressure (filling pressure) of the slurry SL while filling the slurry SL is increased (enhanced) to thereby improve the filling rate of the slurry SL. This is also because it is necessary to take into consideration shrinkage of the slurry SL when it is being dried. As a result, as shown in FIG. 3, the slurry SL is filled into the mold 100 in such a manner that a surface of the slurry SL exists outside of “the top surface 104 a of the frame portion 104 and the each of the top surfaces 103 a of the convexity portions for forming nozzle sections 103 (i.e., plane PL)” by a distance t. All of portions of the slurry SL existing outside of the mold 100 with respect to the plane PL will become a remnant membrane (remained residual film) later.

Meanwhile, as shown in FIG. 3, the porous plate 120 is placed on an “upper surface of a porous sintered metal 130 (i.e., on one of both surfaces of the sintered metal 130)”. The sintered metal 130 is set (held) in a casing 140. The casing 140 is made of a “dense and thermally conductive material”. That is, outer circumferences except its upper surface (i.e., side surfaces and a lower surface) of the sintered metal 130 are covered by the dense casing 140. A communicating pipe 141 for suction is inserted at and through a side portion of the casing 140. The communicating pipe 141 for suction is connected to a vacuum pump which is not shown.

The casing 140 is placed on a hot plate (a heating apparatus) 150. The hot plate 150 generates heat when energized to heat a lower surface of the porous plate 120 (i.e., the other surface, or one portion of the porous plate 120) through the casing 140 and the sintered metal 130.

Subsequently, as shown in FIG. 4, the porous plate 120 and the mold 100 are set (placed) in such a manner that the porous plate 120 (the flat surface 120 u which is an exposed surface of the porous plate 120) opposes (faces) to the mold 100 (the molding surface of the mold 100) while the slurry SL is maintained (or kept, held) between “the flat surface 120 u of the porous plate 120 and the molding surface of the mold 100”. At this time, the mold 100 is pressed (impressed) against the porous plate 120 with an appropriate force.

Consequently, as shown by arrows in FIG. 4, the solvent included in “the slurry SL kept in the mold 100” permeates into the fine pores in the vicinity of the flat surface 120 u of the porous plate 120 (contact surface between the slurry SL and the porous plate 120) by capillarity, and vaporizes (is evaporated). As a result, the slurry SL is dried.

Further, in this step, the aforementioned vacuum pump is driven. Driving the vacuum pump allows gases existing in the porous plate 120 to be discharged (refer to white frame arrow A). Therefore, a pressure in the porous plate 120 becomes lower than the atmospheric pressure (e.g., lower than the atmospheric pressure by 80 kPa). Thus, the solvent included in the slurry SL is sucked into the fine pores of the porous plate 120 (especially, the fine pores in the vicinity of the surface of the porous plate 120) (or, the solvent permeates into the fine pores and is evaporated) efficiently. In such a case, a degree of vacuum (the pressure in the porous plate 120) is preferably 0 to −100 kPa, and more preferably −80 to −100 kPa.

It should be noted that it is more preferable that the sintered metal 130 and the porous plate 120 be sealed up by covering “the exposed surface of the sintered metal 130 and the exposed surfaces of the porous plate 120” with a gas tight film or the like, when the pressure in the fine pores of the porous plate 120 is lowered by driving the vacuum pump. The exposed surface of the sintered metal 130 is a portion of the surfaces of the sintered metal 130 which is not covered by “the casing 140 and the porous plate 120”. The exposed surfaces of the porous plate 120 are portions composed of the side surfaces of the porous plate 120 and a portion of the flat surface (upper surface) 120 u of the porous plate 120 which is not covered by the mold 100 (in actuality, the slurry SL). If “the exposed surface of the sintered metal 130 and the exposed surfaces of the porous plate 120” are not sealed up, the degree of vacuum in the porous plate 120 decreases, and therefore, an efficiency in evaporation of the solvent decreases. Further, a negative pressure is generated at portions from which the solvent of the slurry SL was evaporated, and therefore, air is introduced into the portions. As a result, air holes may be generated in the slurry SL, especially in the vicinity of the porous plate 120. In contrast, as described above, when “the exposed surface of the sintered metal 130 and the exposed surfaces of the porous plate 120” are sealed up, the generation of such air holes can be prevented.

Furthermore, in this step, the hot plate 150 is energized. Therefore, a temperature of the porous plate 120 increases, and thereby the solvent which has permeated into the fine pores of the porous plate 120 can be easily evaporated (or diffused). As a result, the slurry SL is dried and becomes solidified, so that a compact-after-dried 110 (compact 110 which has been dried) is formed between “the mold 100 and the porous plate 120”.

It should be noted that, in this step, the hot plate 150 may be placed at an uppermost position, the casing 140, the sintered metal 130, and the porous plate 120 may be held below the hot plate 150, and the “mold 100 into which the slurry SL is filled” may be pressed against the porous plate 120. That is, the arrangement shown in FIG. 4 may be turned upside down (inverted). This allows the solvent which vaporized to be evaporated (diffused) upwardly in a vertical direction. Therefore, the solvent having small specific gravity which has vaporized can be easily evaporated (diffused), so that the air holes are unlikely to be generated in the slurry SL.

Decreasing the pressure in the fine pores of the porous plate 120 by driving the vacuum pump is optionally performed. Thus, the sintered metal 130 and the casing 140 may be replaced with a simple base. Further, heating the porous plate 120 by the hot plate 150 is also optionally performed. Thus, the hot plate 150 may be omitted. Furthermore, the mold 100 is pressed against the porous plate 120 with the appropriate force when the mold 100 is placed so as to oppose to the porous plate 120, in the present example. However, during “decreasing the pressure in the fine pores of the porous plate 120 by driving the vacuum pump and heating the porous plate 120 by the hot plate 150” after that, no force may be applied to the mold 100, or an appropriate force may be applied to the mold 100 so that a density of the porous plate 120 does not change locally.

Thereafter, when the slurry SL has dried, and therefore, “the compact-after-dried 110” has been formed, “the mold 100, the porous plate 120, and the compact-after-dried 110” are cooled. Then, as shown in FIG. 5, the mold 100 is released (removed) from “the porous plate 120 and the compact-after-dried 110”. That is, a demolding step is performed.

In this demolding step, it is preferable that the vacuum pump be driven so as to decrease the pressure in the sintered metal 130. This allows the sintered metal 130 to hold the porous plate 120 stably, when the mold 100 is removed (during demolding). As a result, it is possible to prevent the porous plate 120 from being lifted up, and thus, a deformation of the porous plate 120 and a deformation of the compact-after-dried 110 (i.e., breakage of the pattern) can be avoided.

Subsequently, the compact 110 is separated from the porous plate 120. As a result, the compact 110 shown in FIG. 6, which is after dried, and before fired, is obtained.

It should be noted that, before the demolding step is performed, the porous plate 120 may be released from the compact 110, and thereafter, a surface of the compact 110 from which the porous plate 120 was released may be fixed using a heat reactive adhesive film or suction, and so on. Thereafter, the demolding step may be performed under such a state to thereby release the mold 100 from the compact 110 to obtain the compact 110 shown in FIG. 6. This allows a pattern of the compact 110 to be fixed by the mold 100 when the porous plate 120 is released, the likelihood of the deformation of or the breakage of the pattern can be decreased.

The thus formed compact 110 has a remnant membrane (remained residual film) RF, as shown in a circle with a dashed line in FIG. 6. The remnant membrane RF is formed of the slurry SL which remained between the top surface 103 a of each of the convexity portions for forming nozzle sections 103 of the mold 100 and the flat surface 120 u of the porous plate 120.

As described above, the compact forming step is a step for forming the compact-after-dried 110 by placing the porous plate 120 and the mold 100 in such a manner that they oppose (face) to each other while the slurry SL is maintained (or kept, held) between “the flat surface 120 u of the porous plate 120 and the molding surface of the mold 100”, and drying the slurry SL through having the solvent included in the slurry SL permeate into the fine pores of the porous plate 120.

(Head-Body-Before-Fired Forming Step)

Subsequently, the remnant membrane RF is removed (eliminated) by a laser processing. That is, as shown in FIG. 7, through holes H are formed in the remnant membrane RF. As a result, the nozzle sections 21 b are completed, and thus, a “head body-before-fired 20A” shown in FIG. 7 is made. FIG. 8 is a partially magnified photograph of the thus manufactured head body-before-fired 20A.

(Firing Step)

In the meantime, a ceramic green sheet to be the vibration plate 30 and a ceramic green sheet to be the liquid storage chamber cover member 40 are prepared, separately. Further, a through hole to be the liquid supply through hole 40 a is formed in the ceramic green sheet to be the liquid storage chamber cover member 40 at an appropriate position. Thereafter, the ceramic green sheet to be the vibration plate 30 and the ceramic green sheet to be the liquid storage chamber cover member 40 are layered (stacked) on the head body-before-fired 20A while aligning them in a planar direction. Subsequently, these are joined by a thermal compression bonding, and the thermal compression bonded layered body is fired after it is degreased. As a result, the head body 20 (fired layered body, a droplet discharge head body-after-fired) having the vibration plate 30 and the liquid storage chamber cover member 40 is completed.

(Piezoelectric Element Forming Step)

Thereafter, according to a well-known method, piezoelectric elements are formed at predetermined positions. For example, the head body 20 and a piezoelectric element including a fired piezoelectric membrane are joined. At this time, the fired piezoelectric membrane is placed on the upper surface of the vibration plate 30. Subsequently, a mask is formed on the piezoelectric element, and fine particles (abrasive grains) are injected/projected to the mask to thereby remove (eliminate) the piezoelectric element on which the mask does not exist. That is, so-called “blast processing” is used to form the piezoelectric elements 50 (refer to, for example, Japanese Patent No. 3340043). By means of these processes, the droplet discharge head 10 is completed. It should be noted that piezoelectric elements which have not been fired may be formed on the vibration plate 30 at predetermined positions, and thereafter, the piezoelectric elements may be fired.

According to the manufacturing method described above, the “compact-after-dried 110” is made by drying the slurry SL using the single mold 100 in the single compact forming step. Therefore, it is unnecessary to form two compacts-after-dried using two molds, and to join the two compacts-after-dried. Thus, the processes can be simplified. In addition, it is unnecessary to join a “metal plate having through holes, each of which is to be communicated with each of the nozzle sections 21 b (discharge hole tip portion forming member which is, for example, a nozzle plate made of SUS, or the like)” to the lower surface 20 a of the droplet discharge head body 20. Thus, the processes can be further simplified. Moreover, it is unnecessary to join the two compacts-after-dried by a pressure bonding while aligning those two compacts, and therefore, the droplet discharge head having a desired shape can easily be manufactured.

It should be noted that as long as the slurry preparing step, the mold preparing step, and the porous plate preparing step are performed before the compact forming step, these steps can be performed in any order.

First Modified Example

In place of “removing the remnant membrane RF (forming the through holes H) by the laser processing” in the head-body-before-fired forming step included in the manufacturing method described above, the remnant membrane RF may be removed by a precision polishing after the compact-after-dried 110 is fired. That is, the remnant membrane RF may be removed by a polishing processing after the compact 110 is fired. This enables to precisely adjust a diameter of each of the tip portion (portion of the opening, droplet discharge opening) of the nozzle sections 21 b, and therefore, the nozzle plate (discharge hole tip portion forming member) which is another member (e.g., SUS, or the like) may not need to be used.

Second Modified Example

In place of “removing the remnant membrane RF (forming the through holes H) by the laser processing” in the head-body-before-fired forming step included in the manufacturing method described above, the remnant membrane RF may be removed (eliminated) by a polishing as shown in FIG. 9, after the slurry SL is dried and solidified, and therefore, the compact-after-dried 110 is formed between “the mold 100 and the porous plate 120” (refer to FIG. 4), and before the mold 100 is released from the compact-after-dried 110 (i.e., before demolding). That is, the compact-after-dried 110 may be polished while the compact-after-dried 110 is maintained (held) in the mold 100 to form the through holes H (refer to FIG. 10).

More specifically, this polishing is performed as follows.

Firstly, when the compact-after-dried 110 has been formed in the mold 100 as shown in FIG. 4, the compact-after-dried 110 is released/separated from the porous plate 120 while the compact-after-dried 110 is maintained in the mold 100.

Subsequently, as shown in FIG. 9, the mold 100 maintaining the compact-after-dried 110 in its inside is held at a back side of the mold 100 by a polishing retainer 400. Then, an exposed surface (remnant membrane RF) of the compact-after-dried 110 is impressed onto (pressed against) the polishing plate 410 while the polishing retainer 400 is reciprocated in a horizontal direction (direction parallel to the flat surface 101 u of the base portion 101 of the mold 100), to thereby perform the polishing. After the polishing is completed (i.e., the remnant membrane RF is removed), demolding is preformed. As a result, a “head body-before-fired 20A” shown in FIG. 10 is made.

Polishing the compact-after-dried 110 in a state in which the compact-after-dried 110 is maintained in the mold 100 (i.e., performing a “polishing process-before-demolding”) in this manner has advantages as follows.

(Advantage 1)

If polishing is performed on a compact-after-fired, grinding sludge and/or abrasive grains may enter into the pressure chambers, and so on. Accordingly, removing (eliminating) step for eliminating them is necessary. In contrast, according to the method described above, the compact-after-dried 110 is polished in the state in which the compact-after-dried 110 is maintained in the mold 100, and therefore, grinding sludge and/or abrasive grains do not enter into the pressure chambers, and so on. Therefore, such a removing (eliminating) step is not necessary. Consequently, the manufacturing method as a whole can be simplified.

(Advantage 2)

Since the polishing is performed with using the back side of the mold 100 (i.e., surface opposite to the molding surface) as a reference, a flatness of the surface to be polished (exposed surface of the compact-after-dried 110) can be easily ensured.

(Advantage 3)

Since the “compact-before-fired 310” has lower hardness compared to a fired body, a polishing rate can be increased. That is, the polishing can be completed within shorter time.

It should be noted that, when the “polishing process-before-demolding” is performed, a material having a high hardness is preferably used for the mold 100, or a DLC (diamond like carbon) treatment is preferably applied to the surfaces of the mold 100.

Third Modified Example

In place of “removing the remnant membrane RF (forming the through holes H) by the laser processing” in the head-body-before-fired forming step included in the manufacturing method described above, the remnant membrane RF may be removed (through holes H are formed) by a “special blast processing using elastic grains (described later)” after the compact-after-dried 110 is fired, to thereby complete the nozzle sections 21 b.

More specifically, in the third modified example, “the ceramic green sheet to be the vibration plate 30 and the ceramic green sheet to be the liquid storage chamber cover member 40” are layered (stacked) on the compact-after-dried 110 from which the remnant membrane RF has not been removed yet, while aligning them in a planar direction. Subsequently, these are joined by a thermal compression bonding, and the thermal compression bonded layered body is fired after it is degreased. As a result, the head body-after-fired 20B (droplet discharge head body-before-fired) as shown in (A) of FIG. 11 is made.

Subsequently, as shown in (B) of FIG. 11, the head body-after-fired 20B is held by a certain retainer, and the “special blast processing using elastic body” is performed for the surface of the remnant membrane RF of the head body-after-fired 20B. As disclosed, for example, in Japanese Laid-Open publication 2006-159402, the blast processing is a method for injecting or projecting polishing agents K, each of which includes “abrasive grains, each having small diameter, made of SIC, or the like” which is fixed to an “elastic base material having a relatively large diameter”, to a “surface of an object to be processed (surface of the remnant membrane RF of the head body-after-fired 20B)” in (with) a direction different from a normal line of the surface of the object to be processed. That is, the polishing agents K are projected in an oblique direction with respect to the surface of the remnant membrane RF of the head body-after-fired 20B. In this case, a diameter Dk of the base material of the polishing agent K is preferably larger than a diameter D of each of the nozzle sections 21 b (diameter D of the portion of the opening (droplet discharge opening) formed by each of the tip portion of the nozzle sections 21 b).

When projecting the polishing agents K having an elasticity, as shown in (C) of FIG. 11, the polishing agents K are squashed on the surface of the head body-after-fired 20B, glide over the surface of the head body-after-fired 20B, and thereafter leave from the surface. During the agents L glide over the surface, the surface of the head body-after-fired 20B is abraded (polished by the abrasive grains). As a result, as shown in (D) of FIG. 11, the remnant membrane RF is removed, so that the nozzle sections 21 b are completed.

According to the blast processing (special blast processing using elastic body), even when the head body-after-fired 20B has small undulation/warpage (deformation, twist) caused by being fired, the droplet discharge head body-after-fired can be polished by a constant amount according to the undulation/warpage. Therefore, a diameter (nozzle diameter) of the tip portion of the nozzle sections 21 b (i.e., the opening for the droplet discharge formed on the surface by each of the nozzle sections 21 b) can be maintained/controlled within a desired range.

In addition, according to the special blast processing using elastic body, a surface roughness of the surface 20 a (refer to FIG. 1) which is the lower surface (exposed surface) of the droplet discharge head body 20 and is in the vicinity of the nozzle sections 21 b (in the vicinity of the opening for the droplet discharge) can be made small. Further, imbalance (difference) of the surface roughness among small regions (areas) of the surface 20 a in the vicinity of the nozzle sections 21 b becomes small. Consequently, a “hydrophilicity of the surface 20 a in the vicinity of the nozzle sections 21 b to the droplets to be discharged” is stabilized (i.e., hydrophilicity imbalance among the regions becomes small). Accordingly, the droplets can be more stably discharged from any of the nozzle sections 21 b. In other words, discharge performances among a plurality of the nozzle sections 21 b can be uniformized. Further, according to the special blast processing using elastic body, a minute burrs can be removed (eliminated) around edges (edges of the openings for discharging the droplets) of the nozzle sections 21 b, and thus, the droplets can be much more stably discharged from any of the nozzle sections 21 b.

Furthermore, according to the special blast processing using elastic body, since the diameter Dk of the polishing agent K (diameter of the base material) is large, it is unlikely that the polishing agents K enter into “hollow cavities of the nozzle sections 21 b”. Accordingly, it is not necessary to include a step for removing them, or it is easy to remove them.

It should be noted that, as described above, it is preferable that the injection/projection direction of the polishing agent be different from 90° (that is, different from the normal line of the surface of the object to be processed, or the direction which is not perpendicular to a wall surface to be processed), in the special blast processing using elastic body. Further, the special blast processing using elastic body can be performed before the mold 100 is released from the compact 110 (i.e., before the demolding), and can also be performed after the mold 100 is released from the compact 110 (i.e., after the demolding).

As described above, according to the method for manufacturing a droplet discharge head in accordance with the embodiment and the modified examples of the present invention, the nozzle section is formed without punching using “a mold and a die”. Accordingly, the nozzle sections have no rough fracture surfaces, and it is unlikely that burrs and cracks are generated in the nozzle sections. As a result, the droplet discharge head capable of stably discharging droplets can be provided.

Further, according to the manufacturing method described above, the pressure chambers 21 are made by forming the slurry using the mold 100. Therefore, the droplet discharge head 10 having an excellent shape accuracy can be manufactured, even if the pressure chambers 21 are miniaturized, and/or a distance between the pressure chambers 21 adjacent to each other is short, and so on.

Further, according to the manufacturing method described above, the nozzle sections 21 b are also made by forming the slurry using the mold 100. Therefore, the surface of each of the nozzle sections 21 b is smooth, and is unlikely to have burrs or the like, as compared with the case in which the nozzle sections are formed by punching using a mold and a die. As a result, the droplet discharge head 10 capable of stably discharging droplets can be provided.

Furthermore, according to the manufacturing method described above, it is not necessary to join a “metal plate having through holes, or the like” to the nozzle sections 21 b of the droplet discharge head body 20. Therefore, the manufacturing processes can be further simplified.

It should be noted that the present invention is not limited to the above embodiments, but various modifications may be adopted within the scope of the invention. 

1. A method for manufacturing a droplet discharge head including a droplet discharge head body having a pressure chamber for storing liquid, a nozzle section communicating with said pressure chamber, including: slurry preparing step for preparing a slurry including ceramic powders, a solvent for said ceramic powders, and an organic material; mold preparing step for preparing a mold including a base portion having at least one flat surface, and a convexity portion having a convexity which stands from said flat surface of said base portion and has the substantially same shape as a liquid chamber including said pressure chamber and said nozzle section, wherein a portion of said flat surface of said base portion at which said convexity portion does not exist and a surface of said convexity portion constitute a molding surface; porous plate preparing step for preparing a porous plate, which has at least one flat surface, and through which gases can pass; head-body-before-fired forming step for forming a droplet discharge head body-before-fired by placing said porous plate and said mold in such a manner that said porous plate and said mold oppose to each other while said slurry is maintained between said flat surface of said porous plate and said molding surface of the mold, and drying said slurry through having said solvent included in said slurry permeate into fine pores of said porous plate; and firing step for firing said droplet discharge head body-before-fired.
 2. The method for manufacturing a droplet discharge head according to claim 1, wherein, said head-body-before-fired forming step includes: polishing-before-demolding step for polishing, in a state in which a compact-after-dried formed of said slurry which was dried in said mold is maintained in said mold, an exposed surface of said compact-after-dried to thereby remove a remnant membrane of said compact-after-dried to complete a portion corresponding to said nozzle section; and demolding step for releasing said mold from said compact-after-dried from which said remnant membrane was removed.
 3. The method for manufacturing a droplet discharge head according to claim 2, wherein, said polishing-before-demolding step is a step for polishing said exposed surface of said compact-after-dried by holding said mold, which maintains said compact-after-dried, at an side opposite to said molding surface by a polishing retainer, and pressing said exposed surface of said compact-after-dried against a polishing plate while said polishing retainer is reciprocated in a direction parallel to said flat surface of said base portion.
 4. The method for manufacturing a droplet discharge head according to claim 1, further including: special blast processing using elastic body step, performed after the firing step, for projecting polishing agents, each including a plurality of abrasive grains being smaller than and fixed to an elastic base material, to said droplet discharge head body-after-fired to thereby remove a remnant membrane of said droplet discharge head body-after-fired to complete a portion corresponding to said nozzle section. 